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Started By
Message
Cold air returns vs hot air
Posted on 8/2/17 at 10:42 am
Posted on 8/2/17 at 10:42 am
I know that two of the hot air returns in my apartment are supposed to get filters because they have the easy access sliders. The other cold air return downstairs, is screwed to the wall, no easy access sliders, and doesn't get a filter. Can an HVAC guy explain the reasoning behind this?
I pretty sure hot air returns are near the ceiling, and cold air is near the floor.
I pretty sure hot air returns are near the ceiling, and cold air is near the floor.
4
Posted on 8/2/17 at 10:44 am to themasterpater
I prefer cold air this time of year.
Posted on 8/2/17 at 10:46 am to themasterpater
I didn't know they were broken out into "hot air" and "cold air". If a return doesn't have a filter, then the filter is somewhere internal, or the design is fubar. ETA: Multiple returns suggests good design. Most houses are starved of returns.
This post was edited on 8/2/17 at 10:48 am
Posted on 8/2/17 at 10:49 am to Spock's Eyebrow
Hot air is near the ceiling to pull hot air out of the room since heat rises. Cold air is near the floor to pull cold air when the space needs to be heated.
Posted on 8/2/17 at 10:50 am to Spock's Eyebrow
It's a 4 story unit. One hot air on the 4th floor, one on the 1st, cold air on the 2nd.
Posted on 8/2/17 at 10:50 am to themasterpater
I understand what you're getting at, but since you're gonna be wrong half the time, I wasn't aware it was done for that reason.
Posted on 8/2/17 at 10:51 am to Spock's Eyebrow
What do you mean?
Posted on 8/2/17 at 10:53 am to themasterpater
My guess is the handler/furnace is on the 2nd, yes?
Posted on 8/2/17 at 10:54 am to themasterpater
You're not always cooling or heating, and with air mixing, I'm not sure it matters. Especially with a single return, I always thought it was about convenience.
Posted on 8/2/17 at 11:00 am to themasterpater
quote:
It's a 4 story unit. One hot air on the 4th floor, one on the 1st, cold air on the 2nd.
OK, ignore me except the part about all returns are filtered unless something is seriously screwed up.
Posted on 8/2/17 at 11:01 am to themasterpater
Air returns used only for heating don't NECESSARILY need a filter.
The main reason for a filter on an AC system isn't to clean the air for you. It's to provide clean air for the evaporator coils. AC systems don't cool by just dropping the temperature. Most of the heat in hot air is tied up in the moisture in the air, so AC systems are designed to dehumidify the air and in the process provide chilled air. They do this by condensing the moisture on the evaporator coils. This water collects on the coils and if the air blowing across them is dusty, the dust gets deposited in the water on the coils. When the coils are deactivated and the water evaporates, it leaves a layer of dust behind. Repeat this over and over, and you make a layer of concrete like material on the coils that greatly inhibits their ability to properly function. The filter in an AC system is there to prevent this. A byproduct is that it also makes the air cleaner for the people in the space.
Heating air doesn't involve condensation. It just heats the air. So, even if you're heating the air with the condensing coils in a heat pump, it's not as critical to filter the air (though still a REALLY good idea) as it is during the cooling cycle because there's no water to make the slurry to make the concrete on the coils.
If you have completely separate heating and cooling, using a furnace or electric coil for heat, then there are no refrigeration coils to worry about in the heating cycle, and filtering is even less necessary from a "protect the equipment" standpoint, though there is going to be an increased fire risk in electric heaters.
The main reason for a filter on an AC system isn't to clean the air for you. It's to provide clean air for the evaporator coils. AC systems don't cool by just dropping the temperature. Most of the heat in hot air is tied up in the moisture in the air, so AC systems are designed to dehumidify the air and in the process provide chilled air. They do this by condensing the moisture on the evaporator coils. This water collects on the coils and if the air blowing across them is dusty, the dust gets deposited in the water on the coils. When the coils are deactivated and the water evaporates, it leaves a layer of dust behind. Repeat this over and over, and you make a layer of concrete like material on the coils that greatly inhibits their ability to properly function. The filter in an AC system is there to prevent this. A byproduct is that it also makes the air cleaner for the people in the space.
Heating air doesn't involve condensation. It just heats the air. So, even if you're heating the air with the condensing coils in a heat pump, it's not as critical to filter the air (though still a REALLY good idea) as it is during the cooling cycle because there's no water to make the slurry to make the concrete on the coils.
If you have completely separate heating and cooling, using a furnace or electric coil for heat, then there are no refrigeration coils to worry about in the heating cycle, and filtering is even less necessary from a "protect the equipment" standpoint, though there is going to be an increased fire risk in electric heaters.
This post was edited on 8/2/17 at 11:05 am
Posted on 8/2/17 at 11:01 am to themasterpater
If you have one blower then the RAGs are common to one system and the RA is being drawn through each RAG all the time.
If two RAGs have a filter and one does not then you must have a filter at the unit to protect the fan and the cool. If you don't it's not set up properly.
If two RAGs have a filter and one does not then you must have a filter at the unit to protect the fan and the cool. If you don't it's not set up properly.
Posted on 8/2/17 at 11:01 am to Sao
Nope ,4th floor, in the crawl space. It's a shittastic design.
4 story townhome so the air conditioner is outside on the ground level, the handler is on the 4th floor.
4 story townhome so the air conditioner is outside on the ground level, the handler is on the 4th floor.
Posted on 8/2/17 at 11:04 am to TigerstuckinMS
quote:
If you have completely separate heating and cooling
Mind blown. Is that really a thing?
Posted on 8/2/17 at 11:06 am to themasterpater
quote:
4 story townhome so the air conditioner is outside on the ground level, the handler is on the 4th floor.
That's a really long copper run.
But if you feel like you need a filter grill on the 2nd, just change it out. It's simple work really. Shouldn't affect flow much if you avoid getting a really dense/expensive filter (overkill there)
Posted on 8/2/17 at 11:08 am to Spock's Eyebrow
quote:
Mind blown. Is that really a thing?
Yeah. Think places that might have a furnace and a dedicated straight AC instead of a heat pump. Boston. Places like that get bitterly cold in the winter and a heat pump is not the best choice to maintain a comfortable indoor temperature when the outside air temp drops very low. So, some other source of heat is more effective and efficient in those conditions. It also gets blisteringly hot and muggy in the summer, so some cooling is wanted, too, so you'll still see an AC, it will just be a straight AC system, not a heat pump.
This post was edited on 8/2/17 at 11:15 am
Posted on 8/2/17 at 11:11 am to TigerstuckinMS
Fascinating.
Posted on 8/2/17 at 11:11 am to doubleb
Yeah I was just curious because the landlord said not to put a filter on it because "it's an intake vent". In and of itself that statement makes no sense because the other intake vents get them. It does seem like it's designed not to receive a filter since the whole grill is screwed down, as opposed to the others where they have slider tabs to easily replace filters.
I do realize that filters primary pupose is to limit build up of dust on the coils and to protect the unit. I'm just not sure why one intake vent seems designed not to get a filter.
I do realize that filters primary pupose is to limit build up of dust on the coils and to protect the unit. I'm just not sure why one intake vent seems designed not to get a filter.
Posted on 8/2/17 at 11:16 am to Spock's Eyebrow
quote:
Fascinating.
Not really. It paid the bills for a while, though.
Posted on 8/2/17 at 11:20 am to themasterpater
quote:
I do realize that filters primary pupose is to limit build up of dust on the coils and to protect the unit. I'm just not sure why one intake vent seems designed not to get a filter.
You may have a filter at the unit as well. If horizontal, at the plenum and coil. If upright, at the base/platform. Take a look
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